During operation of a vehicle, horns installed on the vehicle may be used by drivers to alert people and animals of the vehicle's presence and movement. Many vehicle horns may include a flat diaphragm structure that vibrates at predetermined frequency. The vibration may be controlled by an electromagnetic motor or solid state driver circuit. Other horns may be produced by digital audio signals transmitted by a speaker. In a vehicle horn system, multiple horns or audio emitters may be arranged to produce a chord of more than one frequency. A multiple frequency chord may be more perceptible in an environment with high ambient noise.
In many areas, such as highways and urban environments, heavy car usage may result in a high level of ambient noise or noise pollution from an increased amount of honking horns. Noise pollution may negatively affect the health of individuals living near noisy and high-traffic areas. A constant backdrop of noise may elevate stress, causing an increase in blood pressure or a change in heart rhythm, and may increase the pace of hearing loss. Further, pedestrians and other road user may be less alert to horns directed at them. Noise pollution may also negatively impact nearby wildlife.